Screw Back-Out Following "Open-Door" Cervical Laminoplasty: A Review of 165 Plates

STUDY DESIGN: Retrospective study. PURPOSE: To investigate safety profile of open door laminoplasty plates. OVERVIEW OF LITERATURE: Few reports have documented potential complications related to the use of cervical laminoplasty plates. METHODS: Records and radiographs of consecutive plated laminoplasty patients of one academic surgeon were analyzed. Group 1 had screw back-out, defined as change in screw position, and group 2 did not. RESULTS: Forty-two patients (mean age, 56.9) underwent "open-door" cervical laminoplasty using 165 plates. Mean follow-up was 24 months (range, 12-49 months). Mean Nurick grade improved from 2.1 to 0.9 postoperatively. Cervical lordosis (C2-7) was 12.1° preoperatively and 10.0° postoperatively. Range-of-motion was 27.0° preoperatively and 23.4° postoperatively. Partial screw back-out was noted in 27 of 165 plates (16.4%) and in 34 of 660 screws (5.2%). Of the 34 screws, 27 (79.4%) were at either the most cranial (12/27, 44.4%) or the most caudal (15/27, 55.5%) level. Cranially, 11/12 screws (91.7%) had back-out. Caudally, 9/15 lateral mass screws (60.0%) backed-out versus 6 laminar screws (40.0%). Of the 22 patients with screw back-out, 15 (68.2%) occurred <3 months postoperative and 6 (27.3%) occurred 4-12 months postoperative. No statistical differences were found between group 1 and 2 for age, gender, preoperative and postoperative lordosis, focal sagittal alignment, range-of-motion, or Nurick grade. Despite screw backout in 22 patients, there were no plate dislodgements, laminoplasty closure, or neurological deterioration. CONCLUSIONS: Although screw back-out may occur with the use of cervical laminoplasty plates, the use of these plates without a bone block appears to be safe and reliable. As screw back-out is most common at the cranial and caudal ends of the laminoplasty, we recommend using the maximum number of screws (typically 2 for the lateral mass and 2 for the spinous process) at these levels to secure the plate to the bone.